FORMATION OF UNILAMELLAR LIPOSOMES FROM TOTAL POLAR LIPID EXTRACTS OF METHANOGENS

Unilamellar liposomes were formed by controlled detergent dialysis of mixed micelles consisting of acetone-insoluble total polar lipids extracted from various methanogens and the detergent n-octyl-beta-D-glucopyranoside. The final liposome populations were studied by dynamic light scattering and electron microscopy. Unilamellar liposomes with mean diameters smaller than 100 nm were obtained with lipid extracts of Methanococcus voltae, Methanosarcina mazei, Methanosaeta concilii, and Methanococcus jannaschii (grown at 50-degrees-C), whereas larger (> 100-nm) unilamellar liposomes were obtained with lipid extracts of M. jannaschii grown at 65-degrees-C. These liposomes were shown to be closed intact vesicles capable of retaining entrapped [C-14] sucrose for extended periods of time. With the exception of Methanospirillum hungatei liposomes, all size distributions of the different liposome populations were fairly homogeneous.